MMP9 and cancer: Previous studies have additionally indicated the involvement of ER signaling in the microenvironment of bladder cancer, such as cancer-associated immune cells (e.g., reduction of cancer cell invasion via modulating EMT and CCL2/CCR2/MMP9 signals by ERβ knockdown in co-cultured mast cells [82]) and cancer-associated fibroblasts (e.g., modulation of cancer cell invasion by ERα overexpression/knockdown in co-cultured fibroblasts [83]).